The present invention relates to an optical information recording/reproducing method and a device, and particularly to an optical information recording/reproducing method and a device capable of high-speed, high-density recording of information.
Conventionally known optical information recording mediums include CDs (Compact Discs), DVDs (Digital Versatile Discs), and the like. Among them, CD-R (Compact Disc-Recordable), DVD-R (Digital Versatile Disc-Recordable) and the like are known as a write once type (a postscript type).
CD-R and DVD-R have a basic structure comprising a transparent substrate on which spiral pregroups are formed, a recording layer made of an organic pigment film formed on the substrate, a reflection layer made of a metallic film formed on the recording layer and a protection layer nade of ultraviolet setting resin formed on the reflection layer. And, a laser beam is irradiated from the transparent substrate side to the recording layer to partially decompose the pigment on the recording layer so to record on the disc.
Specifically, when information is to be recorded on the optical recording medium such as CD-R or DVD-R, information to be recorded is recorded by irradiating laser light in a pulse form to the spinning recording medium to partially decompose the pigment of the recording layer so to change optical characteristics to form pits according to a digitized digital signal (recording pulse).
When the aforesaid pits are formed on the optical information recording medium, the intensity of the laser light irradiated while a recording pulse is at a high level is enhanced high, and a state of the recording layer is changed by the laser beam energy to form the pits. For example, in a period when the recording pulse is at a low level, laser light having a low optical intensity required for tracking is irradiated.
Meanwhile, there is also proposed a technology to enable high-speed recording by increasing a rotation speed of the optical information recording medium and quickening the cycle of a digital signal according to the increased rotation speed. And, there is also proposed a technology to record information at a speed faster by 8 to 12 times or at a faster recording speed.
In view of advantages of compatibility with CD and a less unit price per pit than paper, CD-R among the optical information recording mediums is rapidly expanding its market. And, recording devices capable of writing at a recording speed 10 times or more faster than an ordinary speed and corresponding media are also being put on the market in response to demands for high-speed processing.
Besides, it is desired on the market that a larger capacity is provided to correspond with the amount of data processing which is increasing every year, and a capacity of 1.3 GB (Gigabytes) or more with respect to the amount of data for image processing or the like.
CD-R reproducible by the general CD or CD-ROM drive has a maximum recording capacity of 700 MB, and there is no CD-R having a higher capacity available on the market.
DVD-R has substantially the same disc shape as CD and its recordable amount of information is 4.7 GB about 7 times larger than the amount of information recordable on the present CD. Such a medium having a large information recording capacity is expected to contribute to the multimedia information society.
A conventional CD-R previously determines a correction range of heat interference from a pickup having a standard sport diameter and a value experimentally obtained from the standard pickup. When the recording pulse is corrected only in the previously determined range, the heat interference can be almost canceled without considering variations of the pickups and media.
CD-R and DVD-R for high-density recording, however, record information at a higher density than the conventional CD-R, so that the information recording method and information recording device used for CD-R often had problems that an error occurs often in information, or information cannot be recorded properly.
For example, CD-R and DVD-R for high-density recording have a smaller track pitch and a smaller minimum pit length than the conventional CD-R and, therefore, are susceptible to a heat influence when prior and subsequent pits are formed to record information. Therefore, pits may not be formed at desired positions, and jitter is deteriorated when information is reproduced. The same is also applied when recording is performed at a high speed.
Especially, DVD-R has a smaller ratio between the spot diameter and the minimum pit length than the conventional CD-R (about xc2xd in comparison with CD), and variations in the production of pickups and media influence largely upon the characteristics. Therefore, it is necessary to separately determine a correction range for canceling the heat interference with the variations of the production taken into consideration.
The correction range and an amount of correction have a relation of 1 to 1 between the drive device and the medium. And, a sufficient recording/reproducing property was sometimes not attainable if they are not adjusted optimally.
It is an object of the present invention to provide an optical information recording/reproducing method and a device therefor which can optimally record and reproduce information on and from an optical information recording medium such as CD-R or DVD-R for high-density recording.
It is also an object of the present invention to provide an optical information recording/reproducing method which can optimally record information by determining a correction range of heat interference by judging an effective spot diameter so to correct a recording pulse.
It is another object of the present invention to provide an optical information recording/reproducing method which can reproduce information by optimally correcting a reproducing signal by judging an effective spot diameter.
The optical information recording method according to the present invention is an optical information recording/reproducing method which irradiates laser light corresponding to a recording pulse to an optical information recording medium to form a pit-land pattern consisting of pits and lands having a plurality of lengths in integral multiple nT (n is an integer) of a predetermined standard length T so to record information, the method comprising: a first step of irradiating the laser light to the optical information recording medium to obtain a reproducing signal corresponding to the pit-land pattern recorded on the optical information recording medium and judging a relative effective spot diameter of the laser light corresponding to the standard length T according to the reproducing signal, and a second step of specifying a correction range at recording the information according to the effective spot diameter judged in the first step and correcting the recording pulse according to the specified correction range.
The effective spot diameter is a relative value to the standard length T, namely a value determined as an integral multiple of the standard length T and indicates a correction range of heat interference at information recording.
According to the present invention, the recording pulse is corrected by judging the correction range of the heat interference according to the effective spot diameter.
The recording pulse according to the invention controls the energy of the laser light output from, for example, an optical pickup in order to record information by forming the pits and lands having the plurality of lengths in integral multiple nT (n is an integer) of the predetermined standard length T. For example, an EFM (Eight Fourteen Modulation) signal can be used.
The first step separately reads the plurality of pits or lands having the different lengths previously recorded on the optical information recording medium to obtain a plurality of reproducing signals corresponding to the pits or lands having the different lengths, and judges the effective spot diameter according to the length of the pit or land with which amplitudes of the reproducing signals become saturated and constant.
Specifically, the amplitudes of the reproducing signals of the pit or land, namely modulation degrees, are changed depending on the pit or land and the spot diameter of the laser light irradiated onto the optical information recording medium to reproduce.
When the pit or land has a small length to the spot diameter, the modulation degree becomes large and the amplitude of the reproducing signal becomes small. Conversely, when the pit or land has a large length to the spot diameter, the modulation degree becomes large and the amplitude of the reproducing signal becomes large.
The amplitude of the reproducing signal becomes constant and saturated when the length of the pit or land to the spot diameter exceeds a predetermined level.
The present invention judges the effective spot diameter according to the length of the pit or land where the amplitude of the reproducing signal becomes saturated and constant.
The first step obtains an eye pattern of the reproducing signal by reading the plurality of pits or lands having the different lengths previously recorded on the optical information recording medium and determines the effective spot diameter according to the length of the pit or land with which an amplitude of the eye pattern becomes saturated and constant.
Generally, the eye pattern of the reproducing signal is influenced by distortion, noise, intersymbol interference, rotation jitter or the like of the recording pit. But, the length of the pit or land with which the amplitude of the eye pattern becomes saturated and constant can be judged as the effective spot diameter.
The first step reads the predetermined pit-land pattern in which the length of the pit or land previously recorded on the optical information recording medium changes sequentially and judges the effective spot diameter according to the length of the pit or land with which an amplitude of the reproducing signal obtained by the above reading becomes saturated and constant.
Thus, when the effective spot diameter can be judged, the correction range of the recording pulse at recording can be specified according to the effective spot diameter, and the recording pulse can be corrected optimally to record optimally.
And, when the effective spot diameter can be judged, the correction range of the reproducing signal at reproducing can be specified according to the effective spot diameter, and the reproducing signal can be corrected optimally.
In other words, the second step at recording presumes a level of heat interference at recording of the pit or land to be recorded according to the pit-land pattern to be recorded at the front and rear of the pit or land to be recorded and the effective spot diameter judged in the first step, and corrects the recording pulse corresponding to the pit or land to be recorded according to the presumed level of the heat interference.
At this time, the second step can be configured to correct a rising timing or a falling timing of the recording pulse corresponding to the pit to be recorded according to a length of a reference land immediately in front of or behind the pit to be recorded.
The second step can also be configured to correct a rising timing or a falling timing of the recording pulse corresponding to the pit to be recorded according to a length of a reference land immediately in front of the pit to be recorded and a length of a reference pit immediately in front of or behind the reference land. The second step can also be configured to correct a rising timing or a falling timing of the recording pulse corresponding to the pit to be recorded according to the length of the pit to be recorded.
The second step can also be configured to correct a rising timing or a falling timing of the recording pulse corresponding to the pit to be recorded according to a recording speed.
The optical information recording/reproducing method of the present invention is an optical information recording/reproducing method which irradiates laser light corresponding to a recording pulse to an optical information recording medium to form a pit-land pattern consisting of pits and lands having a plurality of lengths in integral multiple nT (n is an integer) of a predetermined standard length T so to record information, the method comprising: a first step of irradiating the laser light to the optical information recording medium to obtain a reproducing signal corresponding to the pit-land pattern recorded on the optical information recording medium and judging a relative effective spot diameter of the laser light corresponding to the standard length T according to the reproducing signal, and a second step of specifying a correction range at reproduction of the information according to the effective spot diameter judged in the first step and correcting the reproducing signal according to the specified correction range.
The effective spot diameter indicates a range to change the amplitude and frequency component of the reproducing signal at reproduction of the information.
Then, the present invention specifies a range giving changes in the amplitude and frequency component of the reproducing signal according to the effective spot diameter so to correct the reproducing signal.
In other words, the second step in reproduction of the information presumes a level of changes in amplitude and frequency component of the reproducing signal at reproduction of the pit or land to be reproduced according to an effective spot diameter judged in the first step and the pit-land pattern recorded at the front and rear of the pit or land to be reproduced and corrects the reproducing signal corresponding to the pit or land to be reproduced according to a presumed level of the changes in the amplitude and frequency component.
The second step can correct the changes in amplitude and frequency component of the reproducing signal by adjusting a gain and a delay amount of the reproducing signal.
A gain of the reproducing signal and a delay amount can be adjusted by a combination of an equalizer and a low-pass filter.
The optical information recording/reproducing device according to the present invention is an optical information recording/reproducing device which irradiates laser light corresponding to a recording pulse to an optical information recording medium to form a pit-land pattern consisting of pits and lands having a plurality of lengths in integral multiple nT (n is an integer) of a predetermined standard length T so to record information, the device comprising: effective spot diameter judging means which irradiates the laser light to the optical information recording medium to obtain a reproducing signal corresponding to the pit-land pattern recorded on the optical information recording medium and judges a relative effective spot diameter of the laser light corresponding to the standard length T according to the reproducing signal, and recording pulse correcting means which specifies a correction range at recording of the information according to the effective spot diameter judged by the effective spot diameter judging means and corrects the recording pulse according to the specified correction range.
The effective spot diameter judging means separately reads the plurality of pits or lands having the different lengths previously recorded on the optical information recording medium and judges the effective spot diameter according to the length of the pit or land with which amplitudes of a plurality of reproducing signals corresponding to the pits or lands having the different lengths obtained by reading become saturated and constant.
The effective spot diameter judging means reads the predetermined pit-land pattern in which the lengths of the pits or lands previously recorded on the optical information recording medium change sequentially and judges the effective spot diameter according to the length of the bit or land with which an amplitude of the reproducing signal obtained by the above reading becomes saturated and constant.
The recording pulse correcting means presumes a level of heat interference at recording of the pit or land to be recorded according to the effective spot diameter judged by the effective spot diameter judging means and the pit-land pattern to be recorded at the front and rear of the pit or land to be recorded and corrects a storage pulse corresponding to the pit or land to be recorded according to the presumed level of heat interference.
The optical information recording/reproducing device according to the present invention is an optical information recording/reproducing device which irradiates laser light corresponding to a recording pulse to an optical information recording medium to form a pit-land pattern consisting of pits and lands having a plurality of lengths in integral multiple nT (n is an integer) of a predetermined standard length T so to record information, the device comprising: effective spot diameter judging means which irradiates the laser light to the optical information recording medium to obtain a reproducing signal corresponding to the pit-land pattern recorded on the optical information recording medium and judges a relative effective spot diameter of the laser light corresponding to the standard length T according to the reproducing signal, and reproducing signal correcting means which specifies a correction range at reproduction of the information according to the effective spot diameter judged by the effective spot diameter detecting means and corrects the reproducing signal according to the specified correction range.
The effective spot diameter judging means separately reads the plurality of pits or lands having the different lengths previously recorded on the optical information recording medium and judges the effective spot diameter according to the length of the pit or land with which amplitudes of the plurality of reproducing signals corresponding to the pits or lands having the different lengths obtained by the above reading becomes saturated and constant.
The effective spot diameter judging means reads the predetermined pit-land pattern in which the lengths of the pits or lands previously recorded on the optical information recording medium change sequentially and judges the effective spot diameter according to the length of the bit or land with which an amplitude of the reproducing signal obtained by the above reading becomes saturated and constant.
The reproducing signal correcting means presumes a level of changes in amplitude and frequency component of the reproduction signal at reproduction of the pit or land to be reproduced according to the effective spot diameter judged by the effective spot diameter judging means and the pit-land pattern to be recorded at the front and rear of the pit or land to be reproduced, and corrects the reproducing signal corresponding to the pit or land to be reproduced according to a presumed level of the changes in the presumed amplitude and frequency component.
The reproducing signal correcting means adjusts a gain of the reproducing signal and a delay mount to correct the changes in the amplitude and the frequency component of the reproducing signal.
The gain and the delay amount of the reproducing signal can be adjusted by a combination of an equalizer and a low-pass filter.